Hot Rod Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
155 Posts
Discussion Starter · #1 ·
Thought I'd share.

New lift in rear of my '64 FJ40 & a swapped in powertrain altered the necessary length of the rear driveshaft. Thus, I needed to shorten the driveshaft 1/2". No concern, as this is a temp fix. When the rig layout is complete & I start the frame off build, I will have a custom shaft built for it. So, no fear, I jumped in.

Step 1 - Determined desired length by measuring flange-to-flange distance at full compression and full droop. Took my full compression distance and added 3/4" to allow for odd compression due to..ummm...jumping in reverse? Had enough stroke in this short shaft that I'd rather be safe than sorry. Thus, I am shortening it 1 and 1/4".

Step 2 - Cut a piece of 2 1/2" angle iron to the length of the tube portion I was going to cut (minus 1 1/4").

Step 3 - Ensured the angle clamped flush to the tube to assist in lining it back up. Used edge of angle to draw a line perpendicular to the cut for a reference point when reassembling the 2 halves, using a paint marker.

Step 4 - Mounted shaft in cold saw, being CERTAIN that it was going to cut at an exact 90-degree angle.

Step 5 - Cut out 1 1 1/8" piece. Width of blade makes this 1 1/4" total.

Step 6 - Chamfered outer edge of two cuts 45 degrees (about 3/32") and deburred insides. Took care not to shorten the pieces while chamfering.

Step 7 - Used angle iron and previous paint marker line to align two halves for reassembly. Clamped in place.

Step 8 - Tacked in 5 spots around shaft.

Step 9 - Used rough scotchbrite wheel on cordless drill to prep surface.

Step 10 - welded. Took some time and 'stitched' small lengths at a time to avoid warpage.

Step 11 - Used same wheel to scuff entire shaft & painted with hammerite.

Sorry, I didn't take pics of every stage...
 

Attachments

·
Member - AMC/Rambler "guru"
Joined
·
1,848 Posts
I've only one tip for any butt welding -- leave a gap the thickness of the rod or wire you're welding with. That ensures 100% penetration. As you go around the arc will produce what looks kind of like an old fashioned keyhole right in front of it).
 

·
Registered
Joined
·
5,920 Posts
I have welded several driveshafts in this manner having good success each time, it works just fine. I must agree 100% with Farna on leaving that gap as he described as this is very important to the ultimate strength of the joint and if properly done it should be strong enough and there is no reason to consider it weak.
 

·
Administrator
Joined
·
10,121 Posts
About 20 yrs ago I remember a magazine had a project vehicle where the drive shaft was shortened in the middle.

When the shaft broke it tore up quite a bit of stuff under the car .

best of luck
 

·
Registered
Joined
·
5,920 Posts
Properly welded there is no reason the shaft should break. Sure it will be weak if it is done wrong but a good sound weld using a torch, TIG or even a MIG in the hands of an expert would have more than sufficient strength and the only problem I see is getting it straight but with attention to detail this should be no problem either. As I said earlier I have done this several times both on auto/truck drive shafts and power shafts used on mining equipment that probably see more abuse than most street driven cars and it worked just fine, it depends on the quality of the weld but it is not at all difficult to do.
 

·
Registered
Joined
·
361 Posts
oldred said:
Properly welded there is no reason the shaft should break. Sure it will be weak if it is done wrong but a good sound weld using a torch, TIG or even a MIG in the hands of an expert would have more than sufficient strength and the only problem I see is getting it straight but with attention to detail this should be no problem either. As I said earlier I have done this several times both on auto/truck drive shafts and power shafts used on mining equipment that probably see more abuse than most street driven cars and it worked just fine, it depends on the quality of the weld but it is not at all difficult to do.

I agree with you. I have done a few of my own shafts, and have never had one break. Good weld, and straight. Also have it balanced.
 

·
Registered
Joined
·
155 Posts
Discussion Starter · #9 ·
Appreciate the input, all. This shaft had been previously mauled at each end when the longer drivetrain was put in. They just didn't take enough out to not 'hit' under full compression. Thus, third time is the charm.

As I said, it is a temp fix. And this isn't my first rodeo. Thanks to all.
 
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top